1. Field of the Invention
The present invention relates to agricultural application systems and in particular to such systems employing multiple segment boom sprayers.
2. Description of Related Art
Cost effective techniques for delivering agricultural chemicals to large size land surface areas have been undergoing continuous development. These systems typically employ a vehicle such as aircraft or a land based vehicle which is either self propelled or towed behind a tractor or the like. In the past, agricultural products to be applied to a land surface area were mixed, diluted or otherwise prepared for spraying in bulk quantities carried on the vehicle in large tanks. The vehicle is driven in a parallel fashion to cover the entire land surface area, one strip at a time. Typically, such coverage techniques require the vehicle to stop at periodic intervals so as to reverse direction, as when the end of a strip is reached. The vehicle is then turned about and is brought to operational speed as quickly as is practical. Most practical vehicle-based agricultural application systems employ a spray boom extending generally perpendicular to the direction of vehicle travel so as to increase the width of the strip formed by each traversal of the vehicle across the land surface area.
Over the years, various attempts have been made to improve the performance of vehicle-based application systems using spray booms. With the development of satellite navigation systems, there has been a recent emphasis in developing electronic controls for application systems which use satellite positional information to vary the dosage of chemical products "on the fly" as a spray vehicle traverses the land area being treated.
Computer-based controls not directly related to satellite navigation have been more intensely explored once a manufacturing commitment was made to provide on board computer capability for application vehicles. For example, U.S. Pat. Nos. 4,530,463; 4,553,702; and 5,337,959 are directed to agricultural spraying operations in which computer controls are applied to varied nozzle sizes and to control other aspects of the spraying operations. Despite these advances, problems inherent in practical agricultural application systems remain. For example, practical agricultural spray booms have grown to substantial sizes, as much 80 feet or more. It is preferred that, once a command to begin spraying is given, that chemical product be discharged from the various nozzles extending along the boom at the same time. It has been observed, however, that nozzles extending along the boom initiate spray delivery at varying times in response to a common control signal. For example, a "W" pattern of chemical concentration exiting the spray boom nozzles as a function of time has been observed. Ideally, the "W" pattern would be converted to a straight line pattern extending perpendicular to the direction of vehicle travel. Attainment of this goal in an economical and reliable manner is still being sought. Of course, these system problems are magnified when applied dosage rates are varied along the length of vehicle travel.